The new cultivar is a product of selection made by the inventors. The new variety was discovered in Rio Oso, Calif. as an individual seedling of unknown parentage, tree demonstrating superior vigor and growth in an orchard with less than ideal cultural conditions. The orchard was composed of seedling rootstocks of Juglans hindsii x regia with the variety ‘Tulare’, U.S. Plant Pat. No. 8,268, grafted on the top. This tree with outstanding growth was selected and observed during May of 2011.
Asexual reproduction of the new cultivar ‘Cliff Clone’ was first performed via tissue culture in a commercial laboratory in Yuba City, Calif. during June of 2014. Subsequent propagation has shown that the unique features of this cultivar are stable and reproduced true to type on successive generations.
Commercial walnut production is a significant and important crop in some regions, and especially in California. A significant challenge to the industry is reduced vigor of trees when planted into orchards where walnut trees have previously been planted. “Replant disorder” is characterized as a complex of fungi, bacteria, and nematodes remaining at damaging levels in the soil after the removal of the previous orchard, preventing new walnut trees from growing in a normal fashion. Developing a rootstock which can impart vigor into “replant” orchards represents a valuable and distinct improvement.
A further identified challenge in the production of commercial walnut trees is Pratylenchus vulnus, the primary nematode responsible for damage to commercial walnut production in California. This damage includes lack of vigor, and marked inconsistent, non-uniform growth. In modern orchard systems, a predictable and uniform tree performance is of high commercial value.